The modem paper and pulp industry provides a wide variety of products, ranging from simple products, such as brown bags from recycled paper, to highly sophisticated products, such as paper-thin highly absorbent layered constructs that often contain a variety of synthetic additives, such as superabsorbent polymers, for use in products such as disposable diapers. Despite the wide range in the level of technology necessary to produce these products, they all have at least one factor in common, namely, all are fabricated from fibers. In some instances, the fibers are entirely of natural origin, whereas in other cases the fibers are synthetic or a mixture of synthetic and natural fibers.
For a variety of reasons, the manufacture of a particular fibrous product frequently requires the production of base stock fibrous sheets, which are then subject to "fibefization" to again produce fibers, and mixtures of fibers, that are then laid in webs for the production of other fibrous products that have a higher value. The production of these value-added products require an efficient mechanism for the fibefization of base stock fibrous sheets. Conventionally, the fiberization of the base stock sheets is carried out in a hammermill that has specific design features to enhance the fiberization process.
U.S. Pat. No. 5,253,815 (commonly owned) shows a hammermill design in which the hammers are configured to minimize dead spaces within the fiberizer to enhance throughput. In this design, a hammermill for fiberizing sheets or mats of fibers includes a housing within which an elongated rotor is positioned. The rotor has a longitudinal axis of rotation and a plurality of hammers radially extend from and are coupled to the rotor. Distal end surfaces of individual hammers sweep out separate cylindrical paths with gaps between the paths swept by other individual hammers. These gaps between the paths typically range from zero to no more than about one-quarter of an inch. At least one inlet is provided through which a base stock board is delivered to the cylindrical paths of the hammers for fiberization. Typically, the feed rate of the base stock board to be fiberized is controlled by a pair of seal rollers that engage either side of the sheet.
It has been a long-standing problem that hammermills that have more than one feed slot for receiving base stock fibrous sheet tend to clog up at a feedpoint, downstream of the first board feed slot that hammers encounter in a rotation cycle, after prolonged use. This necessitates turning off the hammermill, manually unclogging blocked feed slots, and then resuming the fiberizing operation. Not only does this unclogging operation result in incurring additional labor expenses, but the on-stream utilization time of the hammermill is reduced because of the time taken for unclogging operations. This inefficient utilization of expensive capital equipment is especially troublesome when all equipment is fully utilized and an increased demand for fiberizing capacity can only be obtained through purchase of an additional hammermill. To avoid, or at least delay, this capital outlay, it would be desirable to increase the on-stream availability and utilization of the existing fiberizing hammermills to obtain incremental fiberizing capacity.